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36.9Adjustable Frequency DrivesSPA9000/SPN9000/SPI9000 Common DC Bus Drive Products363636363636363636363636363636363636363636363636363636363636Application DescriptionThe common DC bus product portfolio fulfills all solution demands with a flexible architecture.Front end units are selected according to the level of harmonics and power requirements. Typicaldrive system configurations are illustrated the following figures.SPA + Inverters SPN + Inverters Combination Configuration●●ActiveFront End(SPA)3223Inverter23InverterLow harmonics, -P mains≈ +P mains/ P mains ≤∑P INUSuitable for almost everyapplicationProduct ComparisonAdvantages over Conventional Front EndsEaton Front Ends vs. Conventional23InverterNon-RegenerativeFront End●●Non-regenerativeFront End(SPN)Low total mains power,P mains ≤∑P INUSuitable e.g. for smallprocessing line withun- and recoiler, em-stopcoastingNoteConventional regenerative front end (a.k.a. “anti-parallel thyristor bridge”) is not available from Eaton.3223InverterActiveFront End23Inverter23InverterCommon DC BusCommon DC buscomponents are used in amultitude of combinations.Drives which are braking cantransfer the energy directly tothe drives in motoring mode.ConventionalRegenerative Front End Input device Choke (L) Filter (LCL) Choke or auto-transformer (L)Bridge type Diode/thyristor bridge IGBT bridge, two-level type Anti-parallel connected thyristor bridgeType of operation Controlled half-bridge High frequency modulation Firing angle controlled(1.5 to 3.6 kHz)Direction of power Motoring Motoring and regenerating Motoring and regeneratingCharging Constant current External required Usually internalDC voltage Nominal (approx. 1.35alternative U N )THDSimilar to six-pulse bridgenormal